Characterizing Mid-Latitude Ice on Mars

Jesse Berney

I am working on characterizing mid-latitude ice on Mars, in the form of lobate debris aprons (LDA). LDA are features on the edges of massifs and crater rims which show evidence of flow. Radar data from the shallow radar sounder (SHARAD) instrument on the Mars Reconnaissance Orbiter (MRO) indicates that LDA are composed of near-pure water ice due to the amount of energy loss from each pulse. The current theory is that LDA are debris-covered remnant glaciers from an earlier period in Mars’ history, when climactic and orbital conditions preferentially transferred water to the mid-latitudes rather than the poles. The evidence of flow is unique among ice deposits on Mars, suggesting a much greater age for LDA than for the polar ice caps. This idea is supporting by crater counts, which estimate LDA at about 100 million years of age.

My project focuses on understanding the formation of LDA and why they exist where they do. There is a clear latitude dependence between 30 and 60 degrees north and south of the equator. However, there also appears to be some longitudinal variation. The presence of subsurface reflectors within LDA appears to decrease from west to east in the first of my three study areas, Deuteronilus Mensae. My next step is to investigate two other areas with high concentrations of LDA, of similar latitude to Deuteronilus Mensae but widely separated longitudinally. These two areas are called Tempe/Mareotis and Phlegra Montes. If these other two areas show internal reflectors similar to those in Deuteronilus Mensae, that supports the idea that the LDA formed concurrently and probably in multiple glaciation events occurring on a global scale. Variations in dust content of the ice will help me compare the areas. I also intend to investigate whether the local geology of each area might have had more impact on the formation of LDA than global conditions. I will use high-resolution optical images and roughness calculations in order to determine the relative effects of local geology and global climate.